package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, TimeUnit.MINUTES);
    }
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }
    public <R,ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback,Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从redis中查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);//用String返回
        //2.判断商铺是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在则直接返回
            R bean = JSONUtil.toBean(json, type);
            return bean;
        }
        //判断命中的是否是空字符串（上面已经判断过非空的情况了，所以只剩下null或者空字符串的情况）
        if (json != null) {//当前shopJson==""
            //命中了空值，返回错误
            return null;
        }
        //4.不存在则根据id查询数据库
        R r = dbFallback.apply(id);
        //5.数据库里不存在该商铺，返回错误
        if (r == null) {
            //将空值写到redis中
            stringRedisTemplate.opsForValue().set(key, "",CACHE_NULL_TTL, TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }
        //6.存在则写入redis
        this.set(key, r,time, unit);
        //7.返回
        return r;
    }


    //线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR =
            Executors.newFixedThreadPool(10);
    //利用逻辑过期解决缓存击穿问题
    public <R, ID> R queryWithLogicalExpire(String keyPrefix,ID id, Class<R> type, Function<ID,R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1.从redis中查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);//用String返回
        //2.判断商铺是否存在
        if (StrUtil.isBlank(json)) {
            //3.不存在则返回空
            return null;
        }
        //4.命中，需要把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data = (JSONObject)redisData.getData();
        R r = JSONUtil.toBean(data, type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1.未过期，直接返回店铺信息
            return r;
        }
        //5.2.已过期,需要缓存重建
        //6.重建缓存
        //6.1.获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //6.2.判断是否获取锁成功
        if(isLock){
            //6.3.成功获取锁，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //先查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //6.4.返回过期的店铺信息
        return r;
    }

    //尝试获取锁
    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    //释放锁
    private void unLock(String key) {
        stringRedisTemplate.delete(key);
    }
}
